UK Biobank study links whole-body water mass patterns with mortality

Researchers used UK Biobank data to assess whether baseline whole-body water mass (WBWM) and its annual change were associated with all-cause and cause-specific mortality. The analysis included 489,793 participants with baseline WBWM data; median age was 58 years, and median follow-up was 13.7 years. Cox proportional hazards models were used, with baseline WBWM grouped by sex-specific tertiles and change categorized as decrease, stable, or increase. There were 40,139 deaths (8.2%) during follow-up.

Associations between baseline WBWM and all-cause, cardiovascular, and other-cause mortality were V-shaped. Compared with medium WBWM, low WBWM was associated with higher hazards of all-cause mortality (HR 1.069, 95% CI 1.042–1.096), cardiovascular mortality (HR 1.084, 1.022–1.149), and mortality from other causes (HR 1.221, 1.167–1.279). High WBWM was associated with 8.7% higher all-cause, 25.4% higher cardiovascular, and 7.5% higher cancer mortality hazards than medium WBWM. The lowest mortality risk was observed in the medium-and-stable group.

The findings indicate associations in a large observational cohort, not evidence that changing WBWM alters mortality. The authors describe WBWM as a potential health-assessment marker; the study does not establish its value for individual risk prediction or clinical decision-making.